Continuing on the subject of bacteriotherapy, there was a fascinating paper out last month in PLoS Pathogens by Lawley et al. As I said in the last post, C. difficile infection of the gut is bad news, and one of the best cures is fecal transplantation. Lawley et al. describe experiments in a mouse model that closely approximates the situation in humans. They showed that the epidemic strain of C. difficile 027/BI is much more of a terror than other strains, as the bug was highly contagious and liked to overstay its welcome longer than the other strains tested.

Variability in pathogenicity between strains of C. difficile is not surprising, as this has also been shown in humans. But the authors made use of their mouse models to take the work further. By culturing the feces from healthy mice, and using different mixes of the cultured microbes as treatment, they were able to discover a bacterial mixture that worked as well as a fecal transplantation in its ability to reduce C. difficile and restore the healthy microbial community diversity. This result provides a potential treatment for those infected with these highly resistant and virulent strains, and also is one of the first potential live bacterial treatments likely to be developed from microbiome studies.

So, which bacteria were in the mix? They identified the already-known species Staphylococcus warneri, Enterococcus hirae, Lactobacillus reuteri, and also three new species in the genera Anaerostipes, Bacteroidetes, and Enterorhabdus. No doubt this team and others will be busy studying these species, as well as identifying their human counterparts.